German fourth seed Alexander Zverev began his US Open campaign with a composed straight-set victory against American Sam Querrey.

Zverev is looking to add a first Grand Slam title to the Olympic gold he won in Tokyo at the start of August.

The German beat world number one Novak Djokovic in the Olympic semi-finals and the Serb plays later on Tuesday.

Djokovic, 34, begins his bid to win all four Grand Slams in the same year against Danish qualifier Holger Rune in Tuesday's night session on Arthur Ashe Stadium (00:00 BST).

Zverev, who could face Djokovic in the semi-finals, said after his win: "Novak is chasing history but I think the young guys are going to try and get in the way of that and I am looking forward to maybe giving him a challenge as well."

The 2021 French Open semi-finalist took advantage of two error-strewn games from world number 78 Querrey, 33, for late breaks in the first two sets and pulled away in the third for a dominant win.

He will face Albert Ramos-Vinolas in the next round after the Spaniard came through in five sets against France's Lucas Pouille.

Canadian seventh seed Denis Shapovalov stormed into the second round with a 6-2 6-2 6-3 victory over Federico Delbonis, taking one hour and 49 minutes to see off the Argentine.

Sixth seed Matteo Berrettini also made it through in straight sets, with the Italian needing two tie-breaks to overcome Frenchman Jeremy Chardy 7-6 (7-5) 7-6 (9-7) 6-3.

But ninth seed Pablo Carreno Busta went down to American qualifier Maxime Cressy, who served 44 aces to come from two sets down to win 5-7 4-6 6-1 6-4 7-6 (9-7).

Japan's Kei Nishikori, runner-up in 2014, beat Italy's Salvatore Caruso 6-1 6-1 5-7 6-3 and will face Mackenzie McDonald after the American knocked out Belgian 27th seed David Goffin in straight sets.

Russian 25th seed Karen Khachanov also suffered a surprise first-round exit at the hands of South Africa's Lloyd Harris, going down 6-4 1-6 4-6 6-3 6-2 to the 24-year-old world number 46.

Meanwhile, American prospect Sebastian Korda lost the first set of his meeting with Georgia's Nikoloz Basilashvili 6-2 and was 2-1 down in the second before he retired. It was not clear why he could not continue but the 21-year-old withdrew from the Toronto Masters with a back injury earlier this month.

There were also wins for Polish 10th seed Hubert Hurkacz, Italian 13th seed Jannik Sinner and France's Gael Monfils, the 17th seed.